This invention relates to monitoring of cardiac activity, e.g., movement, and in particular by means other than direct recording of the electrical activity of the heart. It is important to know the activity of the heart (particularly the rate and regularity of heart beats) in different situations when normal methods of producing an electrocardiogram are not available or is difficult to use. An electrocardiogram (ECG) is used firstly to diagnose a heart disease or heart damage, but also to evaluate the effects of a heart treatment or activity regulation device (pacemaker).
The electrocardiogram is often used in parallel with acquisition of angiographic images, particularly during surgical operations. Apart from these medical applications, the electrocardiogram signal is also used for the treatment of cardiovascular angiography images. It makes it easy to identify images corresponding to the same phase in different heart cycles. Thus, two synchronous images may be obtained and subtracted from each other, thus eliminating effects of contrast due to unimpregnated tissues, and thereafter by showing contrasts due solely to impregnation from injected contrast material that appeared between the two cycles.
In case the electrocardiogram is not accessible or missing in the angiographic system, it is necessary to provide an equivalent signal form from the available information, i.e., images. An embodiment of the present invention is to circumvent the lack of a true electrocardiogram signal or provide an alternative to the electrocardiogram signal.